linux-stable.git/drivers/char/random.c, branch linux-3.4.y

random: add and use memzero_explicit() for clearing data

2015-02-02T09:04:54+00:00

commit d4c5efdb97773f59a2b711754ca0953f24516739 upstream.

zatimend has reported that in his environment (3.16/gcc4.8.3/corei7)
memset() calls which clear out sensitive data in extract_{buf,entropy,
entropy_user}() in random driver are being optimized away by gcc.

Add a helper memzero_explicit() (similarly as explicit_bzero() variants)
that can be used in such cases where a variable with sensitive data is
being cleared out in the end. Other use cases might also be in crypto
code. [ I have put this into lib/string.c though, as it's always built-in
and doesn't need any dependencies then. ]

Fixes kernel bugzilla: 82041

Reported-by: zatimend@hotmail.co.uk
Signed-off-by: Daniel Borkmann 
Acked-by: Hannes Frederic Sowa 
Cc: Alexey Dobriyan 
Signed-off-by: Theodore Ts'o 
[lizf: Backported to 3.4:
 - adjust context
 - another memset() in extract_buf() needs to be converted]
Signed-off-by: Zefan Li

random: fix accounting race condition with lockless irq entropy_count update

2014-06-07T23:02:14+00:00

commit 10b3a32d292c21ea5b3ad5ca5975e88bb20b8d68 upstream.

Commit 902c098a3663 ("random: use lockless techniques in the interrupt
path") turned IRQ path from being spinlock protected into lockless
cmpxchg-retry update.

That commit removed r->lock serialization between crediting entropy bits
from IRQ context and accounting when extracting entropy on userspace
read path, but didn't turn the r->entropy_count reads/updates in
account() to use cmpxchg as well.

It has been observed, that under certain circumstances this leads to
read() on /dev/urandom to return 0 (EOF), as r->entropy_count gets
corrupted and becomes negative, which in turn results in propagating 0
all the way from account() to the actual read() call.

Convert the accounting code to be the proper lockless counterpart of
what has been partially done by 902c098a3663.

Signed-off-by: Jiri Kosina 
Cc: Theodore Ts'o 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings 
Cc: Qiang Huang 
Signed-off-by: Greg Kroah-Hartman

random: run random_int_secret_init() run after all late_initcalls

2013-10-22T08:02:25+00:00

commit 47d06e532e95b71c0db3839ebdef3fe8812fca2c upstream.

The some platforms (e.g., ARM) initializes their clocks as
late_initcalls for some unknown reason.  So make sure
random_int_secret_init() is run after all of the late_initcalls are
run.

Signed-off-by: "Theodore Ts'o" 
Signed-off-by: Greg Kroah-Hartman

random: mix in architectural randomness in extract_buf()

2012-08-15T15:10:30+00:00

commit d2e7c96af1e54b507ae2a6a7dd2baf588417a7e5 upstream.

Mix in any architectural randomness in extract_buf() instead of
xfer_secondary_buf().  This allows us to mix in more architectural
randomness, and it also makes xfer_secondary_buf() faster, moving a
tiny bit of additional CPU overhead to process which is extracting the
randomness.

[ Commit description modified by tytso to remove an extended
  advertisement for the RDRAND instruction. ]

Signed-off-by: H. Peter Anvin 
Acked-by: Ingo Molnar 
Cc: DJ Johnston 
Signed-off-by: Theodore Ts'o 
Signed-off-by: Greg Kroah-Hartman

random: Add comment to random_initialize()

2012-08-15T15:10:29+00:00

commit cbc96b7594b5691d61eba2db8b2ea723645be9ca upstream.

Many platforms have per-machine instance data (serial numbers,
asset tags, etc.) squirreled away in areas that are accessed
during early system bringup. Mixing this data into the random
pools has a very high value in providing better random data,
so we should allow (and even encourage) architecture code to
call add_device_randomness() from the setup_arch() paths.

However, this limits our options for internal structure of
the random driver since random_initialize() is not called
until long after setup_arch().

Add a big fat comment to rand_initialize() spelling out
this requirement.

Suggested-by: Theodore Ts'o 
Signed-off-by: Tony Luck 
Signed-off-by: Theodore Ts'o 
Signed-off-by: Greg Kroah-Hartman

random: remove rand_initialize_irq()

2012-08-15T15:10:29+00:00

commit c5857ccf293968348e5eb4ebedc68074de3dcda6 upstream.

With the new interrupt sampling system, we are no longer using the
timer_rand_state structure in the irq descriptor, so we can stop
initializing it now.

[ Merged in fixes from Sedat to find some last missing references to
  rand_initialize_irq() ]

Signed-off-by: "Theodore Ts'o" 
Signed-off-by: Sedat Dilek 
Signed-off-by: Greg Kroah-Hartman

random: add tracepoints for easier debugging and verification

2012-08-15T15:10:28+00:00

commit 00ce1db1a634746040ace24c09a4e3a7949a3145 upstream.

Signed-off-by: "Theodore Ts'o" 
Signed-off-by: Greg Kroah-Hartman

random: add new get_random_bytes_arch() function

2012-08-15T15:10:28+00:00

commit c2557a303ab6712bb6e09447df828c557c710ac9 upstream.

Create a new function, get_random_bytes_arch() which will use the
architecture-specific hardware random number generator if it is
present.  Change get_random_bytes() to not use the HW RNG, even if it
is avaiable.

The reason for this is that the hw random number generator is fast (if
it is present), but it requires that we trust the hardware
manufacturer to have not put in a back door.  (For example, an
increasing counter encrypted by an AES key known to the NSA.)

It's unlikely that Intel (for example) was paid off by the US
Government to do this, but it's impossible for them to prove otherwise
  --- especially since Bull Mountain is documented to use AES as a
whitener.  Hence, the output of an evil, trojan-horse version of
RDRAND is statistically indistinguishable from an RDRAND implemented
to the specifications claimed by Intel.  Short of using a tunnelling
electronic microscope to reverse engineer an Ivy Bridge chip and
disassembling and analyzing the CPU microcode, there's no way for us
to tell for sure.

Since users of get_random_bytes() in the Linux kernel need to be able
to support hardware systems where the HW RNG is not present, most
time-sensitive users of this interface have already created their own
cryptographic RNG interface which uses get_random_bytes() as a seed.
So it's much better to use the HW RNG to improve the existing random
number generator, by mixing in any entropy returned by the HW RNG into
/dev/random's entropy pool, but to always _use_ /dev/random's entropy
pool.

This way we get almost of the benefits of the HW RNG without any
potential liabilities.  The only benefits we forgo is the
speed/performance enhancements --- and generic kernel code can't
depend on depend on get_random_bytes() having the speed of a HW RNG
anyway.

For those places that really want access to the arch-specific HW RNG,
if it is available, we provide get_random_bytes_arch().

Signed-off-by: "Theodore Ts'o" 
Signed-off-by: Greg Kroah-Hartman

random: use the arch-specific rng in xfer_secondary_pool

2012-08-15T15:10:28+00:00

commit e6d4947b12e8ad947add1032dd754803c6004824 upstream.

If the CPU supports a hardware random number generator, use it in
xfer_secondary_pool(), where it will significantly improve things and
where we can afford it.

Also, remove the use of the arch-specific rng in
add_timer_randomness(), since the call is significantly slower than
get_cycles(), and we're much better off using it in
xfer_secondary_pool() anyway.

Signed-off-by: "Theodore Ts'o" 
Signed-off-by: Greg Kroah-Hartman

random: create add_device_randomness() interface

2012-08-15T15:10:27+00:00

commit a2080a67abe9e314f9e9c2cc3a4a176e8a8f8793 upstream.

Add a new interface, add_device_randomness() for adding data to the
random pool that is likely to differ between two devices (or possibly
even per boot).  This would be things like MAC addresses or serial
numbers, or the read-out of the RTC. This does *not* add any actual
entropy to the pool, but it initializes the pool to different values
for devices that might otherwise be identical and have very little
entropy available to them (particularly common in the embedded world).

[ Modified by tytso to mix in a timestamp, since there may be some
  variability caused by the time needed to detect/configure the hardware
  in question. ]

Signed-off-by: Linus Torvalds 
Signed-off-by: "Theodore Ts'o" 
Signed-off-by: Greg Kroah-Hartman